1. Field of the Invention
The present invention relates to a throw-away insert used in the milling of right-angle corners and the like and a milling cutter, e.g., an end mill or corner mill, that uses this insert.
2. Description of the Background Art
Japanese Laid-Open Patent Publication Number Hei 11-333616 describes an example of a throw-away insert (also referred to below simply as insert) used with negative/positive orientation to cut right-angle corners. Negative/positive orientation refers to mounting an insert so that a radial rake of the insert is negative and the axial rake is positive.
In the insert disclosed in Japanese Laid-Open Patent Publication Number Hei 11-333616, the upper surface forms a roughly rectangular shape. A ridge line positioned at the intersection of a side surface and an upper surface serves as a main cutting section, and an end surface of a sloped surface axially projected from an end of a body serves as a secondary cutting section. An upper side section of the side surface that forms the main cutting section with the upper surface is shaped in a wave shape to form a main relief face. A lower side section forming a second relief face forms relief angles that change from the starting point to the end point.
The insert of Japanese Laid-open Patent Publication number Hei 11-333616 is mounted in a cutter body so that an end surface of a sloped surface projected axially from the end of the body and the surface of the torsional lower side section of the side surface are secured. However, the lower side section of the side surface with the relief angle that changes from the starting point to the end point forms a torsional surface, making it difficult to produce a mold to form the insert. The production of the cutter body is also difficult since a torsional surface must be formed on the base face of the insert pocket in the cutter used to secure the side surface to accommodate the shape of the lower side section of the side surface. Furthermore, it is difficult to have the torsional side surface of the insert and the torsional base face of the insert pocket in the cutter formed so that they can be tightly secured against each other. Since there inevitably will be error in the shapes of the two members, the securing and attachment precision of the insert to the cutter body will be negatively affected, leading to reduced stability in cutting, reduced cutting precision, and the like.
The object of the present invention is to improve cutting precision while making insert production easier, making the machining of the insert pocket easier, improving the stability of the securing performed by the cutter body, and improving attachment precision.